import 'dart:isolate';
import 'dart:ui';

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:path_provider/path_provider.dart';
import 'package:flutter_downloader/flutter_downloader.dart';
import 'package:permission_handler/permission_handler.dart';
import 'dart:io';

class VideoDownLoad extends StatefulWidget with WidgetsBindingObserver {
  final TargetPlatform platform;

  VideoDownLoad({Key key, this.title, this.platform}) : super(key: key);

  final String title;

  @override
  _VideoDownLoadState createState() => new _VideoDownLoadState();
}

class _VideoDownLoadState extends State<VideoDownLoad> {
  final _videos = [
    {
      'name': 'Big Buck Bunny',
      'link':
      'http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4'
    },
    {
      'name': 'Elephant Dream',
      'link':
      'http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/ElephantsDream.mp4'
    }
  ];

  List<_TaskInfo> _tasks;
  List<_ItemHolder> _items;
  bool _isLoading;
  bool _permissionReady;
  String _localPath;
  ReceivePort _port = ReceivePort();

  @override
  void initState() {
    super.initState();

    _bindBackgroundIsolate();

    FlutterDownloader.registerCallback(downloadCallback);

    _isLoading = true;
    _permissionReady = false;

    _prepare();
  }

  @override
  void dispose() {
    _unbindBackgroundIsolate();
    super.dispose();
  }

  void _bindBackgroundIsolate() {
    bool isSuccess = IsolateNameServer.registerPortWithName(
        _port.sendPort, 'downloader_send_port');
    if (!isSuccess) {
      _unbindBackgroundIsolate();
      _bindBackgroundIsolate();
      return;
    }
    _port.listen((dynamic data) {
      print('UI Isolate Callback: $data');
      String id = data[0];
      DownloadTaskStatus status = data[1];
      int progress = data[2];

      final task = _tasks?.firstWhere((task) => task.taskId == id);
      if (task != null) {
        setState(() {
          task.status = status;
          task.progress = progress;
        });
      }
    });
  }

  void _unbindBackgroundIsolate() {
    IsolateNameServer.removePortNameMapping('downloader_send_port');
  }

  static void downloadCallback(
      String id, DownloadTaskStatus status, int progress) {
    print(
        'Background Isolate Callback: task ($id) is in status ($status) and process ($progress)');
    final SendPort send =
    IsolateNameServer.lookupPortByName('downloader_send_port');
    send.send([id, status, progress]);
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: Builder(
          builder: (context) => _isLoading
              ? new Center(
            child: new CircularProgressIndicator(),
          )
              : _permissionReady
              ? new Container(
            child: new ListView(
              padding: const EdgeInsets.symmetric(vertical: 16.0),
              children: _items
                  .map((item) => item.task == null
                  ? new Container(
                padding: const EdgeInsets.symmetric(
                    horizontal: 16.0, vertical: 8.0),
                child: Text(
                  item.name,
                  style: TextStyle(
                      fontWeight: FontWeight.bold,
                      color: Colors.blue,
                      fontSize: 18.0),
                ),
              )
                  : new Container(
                padding: const EdgeInsets.only(
                    left: 16.0, right: 8.0),
                child: InkWell(
                  onTap: item.task.status ==
                      DownloadTaskStatus.complete
                      ? () {
                    _openDownloadedFile(item.task)
                        .then((success) {
                      if (!success) {
                        Scaffold.of(context)
                            .showSnackBar(SnackBar(
                            content: Text(
                                'Cannot open this file')));
                      }
                    });
                  }
                      : null,
                  child: new Stack(
                    children: <Widget>[
                      new Container(
                        width: double.infinity,
                        height: 64.0,
                        child: new Row(
                          crossAxisAlignment:
                          CrossAxisAlignment.center,
                          children: <Widget>[
                            new Expanded(
                              child: new Text(
                                item.name,
                                maxLines: 1,
                                softWrap: true,
                                overflow:
                                TextOverflow.ellipsis,
                              ),
                            ),
                            new Padding(
                              padding:
                              const EdgeInsets.only(
                                  left: 8.0),
                              child: _buildActionForTask(
                                  item.task),
                            ),
                          ],
                        ),
                      ),
                      item.task.status ==
                          DownloadTaskStatus
                              .running ||
                          item.task.status ==
                              DownloadTaskStatus.paused
                          ? new Positioned(
                        left: 0.0,
                        right: 0.0,
                        bottom: 0.0,
                        child:
                        new LinearProgressIndicator(
                          value: item.task.progress /
                              100,
                        ),
                      )
                          : new Container()
                    ]
                        .where((child) => child != null)
                        .toList(),
                  ),
                ),
              ))
                  .toList(),
            ),
          )
              : new Container(
            child: Center(
              child: Column(
                mainAxisSize: MainAxisSize.min,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  Padding(
                    padding:
                    const EdgeInsets.symmetric(horizontal: 24.0),
                    child: Text(
                      'Please grant accessing storage permission to continue -_-',
                      textAlign: TextAlign.center,
                      style: TextStyle(
                          color: Colors.blueGrey, fontSize: 18.0),
                    ),
                  ),
                  SizedBox(
                    height: 32.0,
                  ),
                  FlatButton(
                      onPressed: () {
                        _checkPermission().then((hasGranted) {
                          setState(() {
                            _permissionReady = hasGranted;
                          });
                        });
                      },
                      child: Text(
                        'Retry',
                        style: TextStyle(
                            color: Colors.blue,
                            fontWeight: FontWeight.bold,
                            fontSize: 20.0),
                      ))
                ],
              ),
            ),
          )),
    );
  }

  Widget _buildActionForTask(_TaskInfo task) {
    if (task.status == DownloadTaskStatus.undefined) {
      return new RawMaterialButton(
        onPressed: () {
          _requestDownload(task);
        },
        child: new Icon(Icons.file_download),
        shape: new CircleBorder(),
        constraints: new BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.running) {
      return new RawMaterialButton(
        onPressed: () {
          _pauseDownload(task);
        },
        child: new Icon(
          Icons.pause,
          color: Colors.red,
        ),
        shape: new CircleBorder(),
        constraints: new BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.paused) {
      return new RawMaterialButton(
        onPressed: () {
          _resumeDownload(task);
        },
        child: new Icon(
          Icons.play_arrow,
          color: Colors.green,
        ),
        shape: new CircleBorder(),
        constraints: new BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.complete) {
      return Row(
        mainAxisSize: MainAxisSize.min,
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          new Text(
            'Ready',
            style: new TextStyle(color: Colors.green),
          ),
          RawMaterialButton(
            onPressed: () {
              _delete(task);
            },
            child: Icon(
              Icons.delete_forever,
              color: Colors.red,
            ),
            shape: new CircleBorder(),
            constraints: new BoxConstraints(minHeight: 32.0, minWidth: 32.0),
          )
        ],
      );
    } else if (task.status == DownloadTaskStatus.canceled) {
      return new Text('Canceled', style: new TextStyle(color: Colors.red));
    } else if (task.status == DownloadTaskStatus.failed) {
      return Row(
        mainAxisSize: MainAxisSize.min,
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          new Text('Failed', style: new TextStyle(color: Colors.red)),
          RawMaterialButton(
            onPressed: () {
              _retryDownload(task);
            },
            child: Icon(
              Icons.refresh,
              color: Colors.green,
            ),
            shape: new CircleBorder(),
            constraints: new BoxConstraints(minHeight: 32.0, minWidth: 32.0),
          )
        ],
      );
    } else {
      return null;
    }
  }

  void _requestDownload(_TaskInfo task) async {
    task.taskId = await FlutterDownloader.enqueue(
        url: task.link,
        headers: {"auth": "test_for_sql_encoding"},
        savedDir: _localPath,
        showNotification: true,
        openFileFromNotification: true);
  }

  void _cancelDownload(_TaskInfo task) async {
    await FlutterDownloader.cancel(taskId: task.taskId);
  }

  void _pauseDownload(_TaskInfo task) async {
    await FlutterDownloader.pause(taskId: task.taskId);
  }

  void _resumeDownload(_TaskInfo task) async {
    String newTaskId = await FlutterDownloader.resume(taskId: task.taskId);
    task.taskId = newTaskId;
  }

  void _retryDownload(_TaskInfo task) async {
    String newTaskId = await FlutterDownloader.retry(taskId: task.taskId);
    task.taskId = newTaskId;
  }

  Future<bool> _openDownloadedFile(_TaskInfo task) {
    return FlutterDownloader.open(taskId: task.taskId);
  }

  void _delete(_TaskInfo task) async {
    await FlutterDownloader.remove(
        taskId: task.taskId, shouldDeleteContent: true);
    await _prepare();
    setState(() {});
  }

  Future<bool> _checkPermission() async {
    if (widget.platform == TargetPlatform.android) {
      PermissionStatus permission = await PermissionHandler()
          .checkPermissionStatus(PermissionGroup.storage);
      if (permission != PermissionStatus.granted) {
        Map<PermissionGroup, PermissionStatus> permissions =
        await PermissionHandler()
            .requestPermissions([PermissionGroup.storage]);
        if (permissions[PermissionGroup.storage] == PermissionStatus.granted) {
          return true;
        }
      } else {
        return true;
      }
    } else {
      return true;
    }
    return false;
  }

  Future<Null> _prepare() async {
    final tasks = await FlutterDownloader.loadTasks();

    int count = 0;
    _tasks = [];
    _items = [];

    _tasks.addAll(_videos
        .map((video) => _TaskInfo(name: video['name'], link: video['link'])));

    _items.add(_ItemHolder(name: 'Videos'));
    for (int i = count; i < _tasks.length; i++) {
      _items.add(_ItemHolder(name: _tasks[i].name, task: _tasks[i]));
      count++;
    }

    tasks?.forEach((task) {
      for (_TaskInfo info in _tasks) {
        if (info.link == task.url) {
          info.taskId = task.taskId;
          info.status = task.status;
          info.progress = task.progress;
        }
      }
    });

    _permissionReady = await _checkPermission();

    _localPath = (await _findLocalPath()) + Platform.pathSeparator + 'Download';

    final savedDir = Directory(_localPath);
    bool hasExisted = await savedDir.exists();
    if (!hasExisted) {
      savedDir.create();
    }

    setState(() {
      _isLoading = false;
    });
  }

  Future<String> _findLocalPath() async {
    final directory = widget.platform == TargetPlatform.android
        ? await getExternalStorageDirectory()
        : await getApplicationDocumentsDirectory();
    return directory.path;
  }
}

class _TaskInfo {
  final String name;
  final String link;

  String taskId;
  int progress = 0;
  DownloadTaskStatus status = DownloadTaskStatus.undefined;

  _TaskInfo({this.name, this.link});
}

class _ItemHolder {
  final String name;
  final _TaskInfo task;

  _ItemHolder({this.name, this.task});
}